Mercaptan management in selective hydrodesulfurization of fcc naphtha

ABSTRACT

A process for reducing the sulfur content of FCC naphtha is described. The process includes introducing a FCC naphtha feed to a selective hydrogenation zone to form a hydrogenated feed. The hydrogenated feed is separated into light fraction and a heavy fraction. The heavy fraction is introduced into a selective hydrodesulfurization zone to form a desulfurized stream which contains mercaptans. The desulfurized stream is separated into a mercaptan rich stream and a mercaptan lean stream. The mercaptan rich stream is treated with a caustic extraction process, a hydrodesulfurization reaction zone, a selective hydrogenation process, an adsorption process, or an ionic liquid extraction process to remove at least a portion of the mercaptan compounds to form a second mercaptan lean stream.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Application No.PCT/US2016/046281 filed Aug. 10, 2016 which application claims benefitof U.S. Provisional Application No. 62/204,534 filed Aug. 13, 2015, nowexpired, the contents of which cited applications are herebyincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The current Tier 2 Vehicle and Gasoline Sulfur Program of the USEnvironmental Protection Agency (EPA) requires new passenger vehicles tomeet stringent emissions standards including a limit of 30 wt ppmsulfur. Beginning in 2017, the Tier 3 Vehicle Emission and FuelStandards Program will establish even stricter standards with a limit of10 wt ppm sulfur. Special processing is needed to obtain these sulfurlevels.

Gasoline from fluid catalytic cracking (FCC) processes comprises up to50 vol % of a refinery's motor gasoline pool, and up to 90% of the motorgasoline pool's sulfur content. Consequently, it is important that thetreatment of this stream not significantly reduce its octanecontribution to the pool.

In order to obtain the needed sulfur levels, the majority of gasolineworldwide obtained from fluid catalytic cracking (FCC) processes isselectively hydrodesulfurized which generally preserves the alkenes andaromatics. Typical processing conditions for hydrodesulfurizationinclude a temperature of about 250° C. to about 315° C. and a pressureof about 1.7 MPa(g) to about 17-26 bar(g) with a supported CoMocatalyst.

However, selective hydrodesulfurization cannot bring down the sulfurlevel down sufficiently to meet the 10 wt ppm due to formation ofrecombinant mercaptans. The H₂S produced during the selectivehydrodesulfurization reaction stage reacts with olefins present in theeffluent to form mercaptans, predominantly butyl mercaptans. Inaddition, the current selective hydrodesulfurization catalytic systemand the operating conditions are not optimized to target the reductionof the recombinant mercaptans in the selective hydrodesulfurizationreaction stage.

Consequently, in order meet this limit, some refiners have added apolishing reactor downstream of the selective hydrodesulfurizationreactor. Typically, the polishing reactor uses a Ni based catalyst withLHSV of about 1 hr⁻¹ and a temperature of about 280° C. to about 380° C.The polishing reactor reduces the mercaptans especially by saturatingthe olefins and thereby reducing the equilibrium mercaptans in thereactor effluent along with hydrodesulfurization of the recombinantmercaptans. However, saturating the olefins reduces the octane content.

Therefore, there is a need for improved processes for desulfurizing FCCgasoline.

SUMMARY OF THE INVENTION

One aspect of the invention is a process for reducing the sulfur contentof full range fluidized catalytic cracker (FCC) naphtha. In oneembodiment, the process includes introducing a FCC naphtha feed to aselective hydrogenation zone in the presence of hydrogen and ahydrogenation catalyst under selective hydrogenation conditions to forma hydrogenated feed. The hydrogenated feed is separated into at leasttwo fractions, a light fraction and a heavy fraction. The heavy fractionis introduced into a selective hydrodesulfurization zone in the presenceof hydrogen and a hydrodesulfurization catalyst under selectivehydrodesulfurization conditions to form a desulfurized stream, thedesulfurized stream containing mercaptans. At least a portion of thedesulfurized stream is separated into at least two streams, a mercaptanrich stream and a first mercaptan lean stream. At least a portion of themercaptan rich stream is treated to remove at least a portion of themercaptan compounds to form a second mercaptan lean stream. A variety ofprocesses can be used to treat the mercaptan rich stream including, butnot limited to, a caustic extraction process, a hydrodesulfurizationreaction zone, a selective hydrogenation process, an adsorption process,and an ionic liquid extraction process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one embodiment of the process of thepresent invention.

FIG. 2 is an illustration of another embodiment of the process of thepresent invention.

FIG. 3 is an illustration of still another embodiment of the process ofthe present invention.

FIG. 4 is an illustration of yet another embodiment of the process ofthe present invention.

FIG. 5 is an illustration of another embodiment of the process of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The sulfur characterization of the selective hydrodesulfurization (HDS)reactor effluent points to the presence of an abundance of butylmercaptans. There are a number of different pathways through whichthiophenes and substituted thiophenes undergo desulfurization.Typically, thiophene desulfurization proceeds along two parallelpathways. The thiophene hydrogenation and hydrogenolysis reactions occursimultaneously to generate cyclic sulfide and cis and trans-2-butene andthen proceed further to 1-butene and butane. This reaction network alsoincludes olefin saturation reactions. Hydrogenolysis and hydrogenationreactions take place on different sites of the catalyst simultaneously.In general, the hydrogenolysis reaction is represented as occurring atthe sigma site, and hydrogenation at the pi site. All the abovepostulates are reflected in experimental selective HDS runs whereequilibrium mercaptans are present due to the recombination of buteneswith the H₂S.

Several approaches have been developed to manage the mercaptans from theselective HDS reactor. They all rely of the fact that butyl mercaptansare rich in the naphtha fraction having a boiling point range of about60° C. to about 120° C. of the selectively hydrotreated naphtha. Thisfraction, or a portion of it, is then treated to remove the mercaptans.Sulfur speciation measured by ASTM D-5623 method of the HDS reactoreffluent stream and 100° C. minus and 100° C. plus splits from thisstream is mentioned in Table 1, and supports the above concept.

TABLE 1 Selective HD S 100° C. − 100° C. + Attribute Unit Rx Effluent¹Cut Cut SPLIT FRACTION Wt % 100 65 35 Sulfur by XRF² Wppm 21 13 52Sulfur by CdCl2/Hg Wppm 16 8.7 31 Wash³ ASTM D-5623 - Sulfur SpeciationSec-Butyl mercaptan Wppm 10.6 5.7 0 n-Butyl mercaptan Wppm 3.4 1.5 02-Methylthiophene Wppm 3.9 1.0 5.9 3-Methylthiophene Wppm 0 0.6 02-Ethyl thiophene Wppm 3.2 0 5.1 Thiophene - BT Wppm 0 4.1 39.9 unknownsHeavies Wppm 0 0 1.1 ¹Selective hydrodesulfurization reactor effluentstream ²Sulfur analysis of stream using x-ray fluorescence ³Sulfuranalysis of stream using x-ray fluorescence after washing stream withCdCl₂ followed by Hg wash

All of the processes begin with the treatment of the FCC naphtha feed ina selective hydrogenation zone to hydrogenate the diolefins in the feed.The hydrogenated feed is then separated in a splitter column into atleast two fractions, a light fraction and a heavy fraction. In someembodiments, the light fraction has a boiling point in the range of lessthan about 60° C., and the heavy fraction has a boiling point in therange of greater than about 60° C. In other embodiments, the lightfraction has a boiling point in the range of less than about 65° C., andthe heavy fraction typically has a boiling point in the range of greaterthan about 65° C.

The heavy fraction is sent to the selective hydrodesulfurization zonewhere the sulfur in the feed is converted to hydrogen sulfide, and someof the hydrogen sulfide further reacts with olefins in the feed to formmercaptides.

The effluent from the selective hydrodesulfurization zone is separatedinto a least two streams, a mercaptan rich stream and a mercaptan leanstream. In some embodiments, there are two mercaptan lean streams, a lowboiling mercaptan lean stream with a boiling point range lower than thatof the mercaptan rich stream and a high boiling lean mercaptan streamwith a boiling point range greater than that of the mercaptan richstream.

The mercaptan rich stream is then treated to remove the mercaptans. Inone embodiment, a mercaptan rich stream is sent to a caustic extractionzone to remove the mercaptans. The mercaptan free effluent stream fromthe caustic extraction zone can be sent to the gasoline pool. In anotherembodiment, the mercaptan rich stream is treated in a polishing reactorto reduce the level of mercaptans. By sending a concentrated mercaptanrich feed to the polishing reactor, the size of the polishing reactorcan be reduced by a significant amount, in some cases as much as 75-80%.Another embodiment involves sending the mercaptan rich stream to theupstream selective hydrogenation reactor which converts the mercaptansinto heavy disulfides. In this way, a separate polishing zone isavoided. In another embodiment, the mercaptan rich stream is treated inan adsorbent zone to reduce the mercaptans. Another possibility is totreat the mercaptan rich stream in an ionic liquid extraction zone. Theionic liquid can be regenerated as needed and recycled to the extractionzone.

The light fraction from the selective hydrodesulfurization zone can havea boiling point of less than about 60° C., or less than about 65° C. Thelight fraction 140 typically has a T5 boiling point of about 0° C. toabout 25° C., a T95 boiling point of about 50° C. to about 80° C., and afinal boiling point of about 85° C. to about 100° C. The heavy fractionfrom the selective hydrodesulfurization zone can have a boiling point inthe range of about 60° C. to about 220° C., about 65° C. to about 220°C., about 60° C. to about 200° C., or about 65° C. to about 200° C., forexample. The heavy fraction typically has a T5 boiling point of about50° C. to about 80° C., a T95 boiling point of about 160° C. to about220° C., and a final boiling point of greater than about 220° C. toabout 220° C.

This heavy fraction could be fractionated into a mercaptan rich streamwith a boiling point in the range of about 60° C. to about 120° C., orabout 60° C. to about 100° C., or about 65° C. to about 120° C., orabout 65° C. to about 100° C., and a mercaptan lean stream with aboiling point in the range of about 100° C. to about 220° C., about 120°C. to about 220° C., or about 100° C. to about 200° C., or about 120° C.to about 200° C. In some embodiments, the mercaptan rich stream has a T5boiling point of about 60° C. to about 70° C., a T95 boiling point ofabout 90° C. to about 100° C., and a final boiling point of about 100°C. to about 120° C. In some embodiments, the mercaptan lean stream has aT5 boiling point of about 120° C. to about 140° C., a T95 boiling pointof about 190° C. to about 210° C., and a final boiling point of about200° C. to about 220° C. In some embodiments, the mercaptan rich streamhas a T5 boiling point of about 60° C. to about 70° C., a T95 boilingpoint of about 90° C. to about 100° C., and a final boiling point ofabout 100° C.

Alternatively, the desulfurized stream could be divided into a lowboiling mercaptan lean stream with a boiling point in the range of about60° C. to about 85° C., or about 65° C. to about 85° C., a mercaptanrich stream with a boiling point in the range of about 85° C. to about120° C., or about 85° C. to about 100° C., and a high boiling mercaptanlean stream with a boiling point in the range of about 100° C. to about220° C., or about 120° C. to about 220° C., or about 100° C. to about200° C., or about 120° C. to about 200° C. In some embodiments, the lowboiling mercaptan lean stream has a T5 boiling point of about 60° C. toabout 65° C., a T95 boiling point of about 75° C. to about 85° C., and afinal boiling point of about 80° C. to about 90° C. In some embodiments,the mercaptan rich stream has a T5 boiling point of about 80° C. toabout 90° C., a T95 boiling point of about 90° C. to about 100° C., anda final boiling point of about 100° C. to about 120° C. In someembodiments, the high boiling mercaptan lean stream has a T5 boilingpoint of about 100° C. to about 120° C., a T95 boiling point of about180° C. to about 200° C., and a final boiling point of about 200° C. toabout 220° C. In some embodiments, the mercaptan rich stream has a T5boiling point of about 80° C. to about 90° C., a T95 boiling point ofabout 90° C. to about 100° C., and a final boiling point of about 100°C.

One embodiment of the process 100 is illustrated in FIG. 1. The fullrange fluidized catalytic cracker (FCC) naphtha feed 105 and hydrogenstream 110 are introduced into a selective hydrogenation zone 115. Thehydrogen 110 can be a recycle hydrogen stream 125.

The selective hydrogenation zone 115 is normally operated at relativelymild hydrogenation conditions. These conditions will normally result inthe hydrocarbons being present as liquid phase materials. The reactantswill normally be maintained under the minimum pressure sufficient tomaintain the reactants as liquid phase hydrocarbons. A broad range ofsuitable operating pressures therefore extends from about 276 kPa(g) toabout 5516 kPa(g) (about 40 psig to about 800 psig), or about 345 kPa(g)to about 2069 kPa(g) (about 50 and 300 psig). A relatively moderatetemperature between about 25° C. and about 350° C. (about 77° F. toabout 662° F.), or about 50° C. and about 200° C. (about 122° F. toabout 392° F.) is typically employed. The liquid hourly space velocityof the reactants through the selective hydrogenation catalyst should beabove about 1.0 hr⁻¹, or above about 5.0 hr⁻¹, or between about 5.01hr⁻¹ and about 35.0 hr⁻¹. Another variable operating condition is theratio of hydrogen to diolefinic hydrocarbons maintained within theselective hydrogenation zone 115. The amount of hydrogen required toachieve a certain conversion is believed dependent upon both reactortemperature and the molecular weight of the feed hydrocarbons. To avoidthe undesired saturation of a significant amount monoolefinichydrocarbons, there should be less than 2.0 times the stoichiometricamount of hydrogen required for the selective hydrogenation of thediolefinic hydrocarbons which are present in the liquid phase processstream to monoolefinic hydrocarbons. Preferably, the mole ratio ofhydrogen to diolefinic hydrocarbons in the material entering the bed ofselective hydrogenation catalyst is maintained between 1:1 and 1.8:1. Insome instances, it may be desirable to operate with a less thanstoichiometrically required amount of hydrogen, with mole ratios down to0.75:1 being acceptable. The optimum set of conditions will of coursevary depending on such factors as the composition of the feed stream andthe degree of saturation of diolefinic hydrocarbons which it is desiredto perform.

Any suitable catalyst which is capable of selectively hydrogenatingdiolefins in a naphtha stream may be used. Suitable catalysts include,but are not limited to, a catalyst comprising copper and at least oneother metal such as titanium, vanadium, chrome, manganese, cobalt,nickel, zinc, molybdenum, and cadmium or mixtures thereof. The metalsare preferably supported on inorganic oxide supports such as silica andalumina, for example.

In some embodiments, the catalyst is employed in a fixed bed reactorcontaining a cylindrical bed of catalyst through which the reactantsmove in a vertical direction. Other embodiments use trickle bedreactors. In some embodiments, the reactants flow upward through thereactor, while other embodiments use a downflow arrangement. The subjectcatalyst may be present within the reactor as pellets, spheres,extrudates, irregular shaped granules, etc. To employ the subjectcatalyst, the reactants would be preferably brought up to the desiredinlet temperature of the reaction zone, admixed with hydrogen and thenpassed into and through the reactor. Alternatively, the reactants may beadmixed with the desired amount of hydrogen and then heated to thedesired inlet temperature. In either case, the effluent of the reactionzone may be passed into a product recovery facility for the removal ofresidual hydrogen or may be passed directly into downstream productutilization zones if the presence of the residual hydrogen isacceptable. Hydrogen may be removed by flashing the effluent stream to alower pressure or by passing the effluent stream into a strippingcolumn.

The hydrogenated effluent 130 is sent to a splitter column 135 where itis separated into a light fraction 140 and a heavy fraction 145. Thelight fraction 140 typically has a boiling point in the range of lessthan about 65° C., and the heavy fraction 145 typically has a boilingpoint in the range of greater than about 65° C.

The heavy fraction 145 is combined with a hydrogen-rich stream 150 andintroduced into a selective hydrodesulfurization zone 155 to selectivelyremove sulfur. The selective hydrodesulfurization zone 155 contains ahydrotreating catalyst (or a combination of hydrotreating catalysts) andoperated at selected hydrotreating conditions effective to convert amajority of the sulfur in the feed to hydrogen sulfide and minimizesaturation of olefins at the same time. In general, such selectiveconditions include a temperature from about 260° C. (500° F.) to about315° C. (600° F.), a pressure from about 0.69 MPa (100 psig) to about3.45 MPa (500 psig), a liquid hourly space velocity of the freshhydrocarbonaceous feedstock from about 0.5 hr⁻¹ to about 10 hr⁻¹. Otherhydrotreating conditions are also possible depending on the particularfeed stocks being treated. The selective hydrodesulfurization zone 155may contain a single reactor or multiple reactors and each reactor maycontain one or more reaction zones with the same or different catalyststo convert sulfur and nitrogen to hydrogen sulfide and ammonia.

Suitable hydrodesulfurization catalysts are any known conventionalhydrotreating catalysts and include those which are comprised of atleast one Group VIII metal (preferably iron, cobalt and nickel, morepreferably cobalt and/or nickel) and at least one Group VI metal(preferably molybdenum and tungsten) on a high surface area supportmaterial, preferably alumina. Other suitable hydrotreating catalystsinclude zeolitic catalysts, as well as noble metal catalysts where thenoble metal is selected from palladium and platinum. It is within thescope of the processes herein that more than one type of hydrotreatingcatalyst be used in the same reaction vessel. The Group VIII metal istypically present in an amount ranging from about 0.5 to about 20 weightpercent, preferably from about 0.5 to about 10 weight percent. The GroupVI metal will typically be present in an amount ranging from about 1 toabout 25 weight percent, and preferably from about 1 to about 12 weightpercent. While the above describes some exemplary catalysts forhydrotreating, other hydrotreating and/or hydrodesulfurization catalystsmay also be used depending on the particular feedstock and the desiredeffluent quality.

The conditions in the selective hydrodesulfurization zone 155 areeffective to convert greater than about 50 percent of the sulfur in theheavy fraction 145 to hydrogen sulfide and, preferably, about 60 toabout 80 percent of the sulfur to hydrogen sulfide. At the same time,the selected conditions disfavor olefin saturation to generally maintainthe octane level. However, at these conditions, some of the hydrogensulfide produced reacts to form mercaptans. These reactions are oftencalled reversion or recombination reactions.

The effluent 160 from the selective hydrodesulfurization zone 155 canhave a boiling point in the range of about 60° C. to about 220° C., orabout 65° C. to about 220° C., or about 60° C. to about 200° C., orabout 65° C. to about 200° C., for example. In some embodiments, theeffluent 160 can have a T5 boiling point of about 60° C. to about 70°C., a T95 boiling point of about 160° C. to about 200° C., and a finalboiling point of about 200° C. to about 220° C. or greater.

The effluent 160 from the selective hydrodesulfurization zone 155 issent to a separator 165 where it is separated into the hydrogen richstream 170 and a liquid stream 175.

In some embodiments, one portion of hydrogen rich stream 170 compriseshydrogen-rich stream 150 and the remainder comprises recycle hydrogenstream 125. Make-up hydrogen 120 can be added to hydrogen rich stream170 as needed.

Liquid stream 175 is sent to a fractionation zone 180 where it isseparated into at least two streams. As illustrated in FIG. 1, liquidstream 175 is separated into a mercaptan rich stream 185 taken as a sidecut stream and a first mercaptan lean stream 190 taken from a bottoms ofthe fractionation zone 180. In this embodiment, the mercaptan richstream 185 has a boiling point in the range of about 60° C. to about120° C., or about 60° C. to about 100° C., or about 65° C. to about 120°C., or about 65° C. to about 100° C. The first mercaptan lean stream 190has a boiling point in the range of about 100° C. to about 220° C., orabout 120° C. to about 220° C., or about 100° C. to about 200° C., orabout 120° C. to about 200° C. In some embodiments, the mercaptan richstream 185 has a T5 boiling point of about 60° C. to about 70° C., a T95boiling point of about 90° C. to about 100° C., and a final boilingpoint of about 100° C. to about 120° C. In some embodiments, themercaptan lean stream 190 has a T5 boiling point of about 120° C. toabout 140° C., a T95 boiling point of about 190° C. to about 210° C.,and a final boiling point of about 200° C. to about 220° C.

The mercaptan rich stream 185 is sent to a caustic extraction zone 195to remove the mercaptans. A sulfur lean caustic stream 200 enters thecaustic extraction zone 195 and contacts the mercaptan rich stream 185.The caustic extraction process may utilize any alkaline reagent which iscapable of extracting mercaptans from the feed stream at practicaloperating conditions and which may be regenerated in the mannerdescribed. A preferred alkaline reagent comprises an aqueous solution ofan alkaline metal hydroxide, such as sodium hydroxide or potassiumhydroxide. Sodium hydroxide, commonly referred to as caustic, may beused in concentrations of from 1 to 50 wt. %, with a preferredconcentration range being from about 5 to about 25 wt. %. Optionally,there may be added an agent to increase the solubility of the mercaptansin the solution, typically methanol or ethanol although others such as aphenol, cresol or butyric acid may be used.

The conditions employed in the caustic extraction zone 195 may varygreatly depending on such factors as the nature of the hydrocarbonstream being treated and its mercaptan content, etc. In general, theextraction may be performed at an ambient temperature above about 15.6°C. (about 60° F.) and at a pressure sufficient to ensure liquid stateoperation. The pressure may range from atmospheric up to about 6.9 MPa(g) (about 1000 psig) or more, but a pressure in the range of from about345 kPa(g) to about 1034 kPa(g) (about 50 psig to about 150 psig) ispreferred.

A second consideration is that the pressure chosen should ensure anadequate amount of oxygen is dissolved in the alkaline stream in thedownstream oxidation step (not shown), which if practical is preferablyoperated at substantially the same pressure as the caustic extractionzone 195 after normal process flow pressure drops are taken intoconsideration. The temperature in the caustic extraction zone 195 isdesirably in the range of about 10° C. to about 121° C. (about 50° F. toabout 250° F.), or about 26.7° C. to about 48.9° C. (about 80° F. toabout 120° F.). The ratio of the volume of the alkaline solutionrequired per volume of the feed stream will vary depending on themercaptan content of the feed stream. Normally this ratio will bebetween 0.01:1 and 1:1, although other ratios may be desirable. Optimumextraction in this liquid system is obtained with a velocity through theperforations of from about 5 to about 10 feet per second. Essentiallyall of the extractable mercaptans should be transferred to the alkalinesolution from the feed stream. As used herein, the term “essentiallyall” is intended to refer to at least 95% and preferably 98% of all thematerial referred to.

The mercaptans are transferred from the mercaptan rich stream 185 to thesulfur lean caustic stream 200, resulting in a second mercaptan leanstream 205 and a sulfur rich caustic stream 210.

The sulfur rich caustic stream 210 can be sent for treatment to removethe sulfur (not shown) and recycled to the caustic extraction zone 195,if desired.

The second mercaptan lean stream 205 can be combined with the firstmercaptan lean stream 190 to form a combined mercaptan lean stream 215.In some embodiment, light fraction 140 can be combined with the firstmercaptan lean stream 190, the second mercaptan lean stream 205, orboth.

The combined mercaptan lean stream 215 can be sent to the gasoline pool.

There is also an overhead stream 220, which is condensed and separatedin a separator 225 into a gas stream 230 and a liquid stream 235 whichis refluxed to the fractionation zone 180.

In this approach, the olefins present in the naphtha fraction having aboiling point in the range of about 60° C. to about 120° C. in themercaptan rich stream 185 taken from the side of the fractionation zone180 are retained.

Alternatively, the liquid stream 175 from the separator 165 could beseparated into a mercaptan rich stream and a low boiling first mercaptanlean stream, and a high boiling first mercaptan lean stream, asdiscussed below in regard to FIG. 2.

In the process 300 shown in FIG. 2, the mercaptan rich stream is treatedin a polishing reactor to reduce the mercaptans.

The FCC naphtha feed 105 is hydrogenated in the selective hydrogenationzone 115, separated into a light fraction 140 and a heavy fraction 145in splitter column 135, and desulfurized in selectivehydrodesulfurization zone 155 in the same way as described above withrespect to FIG. 1.

The effluent 160 from the selective hydrodesulfurization zone 155 issent to separator 165, which is a divided wall separator. The dividedwall separator 165 has a wall 305 dividing it in two sections 310, 315.The effluent 160 enters section 310 where it is separated intohydrogen-rich stream 170 and liquid stream 175.

Liquid stream 175 is sent to fractionation zone 180 where it isseparated into a low boiling first mercaptan lean stream 320, amercaptan rich stream 325, and a high boiling first mercaptan leanstream 330. The low boiling first mercaptan lean stream 320 has aboiling point range lower than the boiling point range of the mercaptanrich stream 325, while the high boiling first mercaptan lean stream 330has a boiling point range greater than the mercaptan rich stream 325.For example, the low boiling mercaptan lean stream 320 could have aboiling point in the range of about 60° C. to about 85° C., or about 65°C. to about 85° C., the mercaptan rich stream 325 could have a boilingpoint in the range of about 85° C. to about 120° C., or about 85° C. toabout 100° C., and the high boiling mercaptan lean stream 330 could havea boiling point in the range of about 100° C. to about 220° C., or about120° C. to about 220° C., or about 100° C. to about 200° C., or about120° C. to about 200° C. In some embodiments, the low boiling mercaptanlean stream 320 has a T5 boiling point of about 60° C. to about 65° C.,a T95 boiling point of about 75° C. to about 85° C., and a final boilingpoint of about 80° C. to about 90° C.). In some embodiments, themercaptan rich stream 325 has a T5 boiling point of about 80° C. toabout 90° C., a T95 boiling point of about 90° C. to about 100° C., anda final boiling point of about 100° C. to about 120° C. In someembodiments, the high boiling mercaptan lean stream 330 has a T5 boilingpoint of about 100° C. to about 120° C., a T95 boiling point of about180° C. to about 200° C., and a final boiling point of about 200° C. toabout 220° C.

The mercaptan rich stream 325 and a hydrogen rich stream 335 are sent toa polishing reactor (e.g., a hydrodesulfurization reactor) 340. Thehydrogen rich stream 335 can be a portion of the hydrogen rich stream170 from the divided wall separator 165.

The polishing reactor 340 contains a desulfurization catalyst. Suitablecatalysts include, but are not limited to nickel, nickel and molybdenum,zeolitic catalysts, and noble metal catalysts, e.g. platinum orpalladium. In general, the polishing reactor 340 is operated at atemperature in the range of about 280° C. to about 380° C., and apressure in the range of about 350 kPa(g) to about 3450 kPa(g).

The desulfurized effluent 345 from the polishing reactor 340 is sent tosection 315 of the divided wall separator 165 where it is separated intothe hydrogen rich stream 170 and liquid stream 350.

Liquid stream 350 is sent to a stripping zone 355 to remove gases 360forming a third mercaptan lean stream 365. The third mercaptan leanstream 365 can be combined with one or more of the low boiling firstmercaptan lean stream 320, the high boiling mercaptan lean stream 330,and the light fraction 140 from the splitter column 135 to form acombined mercaptan lean stream 370.

By sending a concentrated mercaptan rich stream 325 to the polishingreactor 340, the size of the polishing reactor 340 can be reduced by asignificant amount, in some cases as much as 75-80%. In this embodiment,the low boiling mercaptan lean stream 320 which has a boiling pointrange of about 60° C. to about 85° C. is not sent to polishing reactor340 which results in the olefins present in this fraction beingretained.

Alternatively, the liquid stream 175 can be separated into a mercaptanrich stream and a mercaptan lean stream as described above in FIG. 1,rather than a mercaptan rich stream and at least two mercaptan leanstreams.

In the process 400 shown in FIG. 3, the mercaptan rich stream is treatedby recycling it to the selective hydrogenation zone 115 which convertsthe mercaptans into heavy disulfides. In this way, a separate polishingzone is avoided.

The FCC naphtha feed 105 is hydrogenated in the selective hydrogenationzone 115, separated into a light fraction 140 and a heavy fraction 145in splitter column 135, desulfurized in selective hydrodesulfurizationzone 155, separated into hydrogen-rich stream 170 and liquid stream 175in the same way as described above with respect to FIG. 1.

The liquid stream 175 is sent to the fractionation zone 180 where it isseparated into a low boiling first mercaptan lean stream 405, amercaptan rich stream 410, and a high boiling first mercaptan leanstream 415.

The mercaptan rich stream 410 is sent to the selective hydrogenationzone 115 to be reprocessed.

The flow rates of the mercaptan rich stream 410 and the high boilingfirst mercaptan lean stream 415 can be controlled with a ratiocontroller 420.

The low boiling first mercaptan lean stream 405 can be combined with oneor more of the high boiling first mercaptan lean stream 415 and thelight fraction 140 from the splitter column 135 to form a combinedmercaptan lean stream 425.

Alternatively, the liquid stream 175 can be separated into a mercaptanrich stream and a mercaptan lean stream as described above in FIG. 1,rather than a mercaptan rich stream and at least two mercaptan leanstreams.

In the process 500 shown in FIG. 4, the mercaptan rich stream is treatedby passing it on the adsorption zone 520.

The FCC naphtha feed 105 is hydrogenated in the selective hydrogenationzone 115, separated into a light fraction 140 and a heavy fraction 145in splitter column 135, desulfurized in selective hydrodesulfurizationzone 155, separated into hydrogen-rich stream 170 and liquid stream 175in the same way as described above with respect to FIG. 1.

The liquid stream 175 is sent to the fractionation zone 180 where it isseparated into a low boiling first mercaptan lean stream 505, amercaptan rich stream 510, and a high boiling first mercaptan leanstream 515.

The mercaptan rich stream 510 is sent to an adsorption zone 520. Theadsorption zone 520 contains one or more adsorbent beds containing anadsorbent. The adsorbent can be regenerable or non-regenerable.

Suitable adsorbents include, but are not limited to nickel zeolite Y,nickel exchanged zeolite X, molybdenum exchanged zeolite X, a smectiteclay having a surface area of at least 150 m²/g, and mixtures thereof.Zeolite X belongs to the faujasite family of zeolites. Its synthesis wasfirst reported in U.S. Pat. No. 2,882,244 which is incorporated byreference. Zeolite X has the empirical formula:

0.9+−0.2 M_(2/n)O:Al₂O₃:2.5+−SiO₂:YH₂O

where M is an alkali or alkaline earth metal, “n” is the valence of Mand “Y” has a value up to 8. Briefly, zeolite X is prepared by forming areaction mixture containing reactive sources of the components, reactingthe mixture at a temperature of about 21° C. to about 120° C. for a timeof about 1 hours to about 100 hours. Zeolite X is usually synthesized inthe sodium form. That is, sodium is the counter ion present in the poresof the zeolite.

The synthesis of zeolite Y is described in U.S. Pat. No. 3,130,007 whichis incorporated by reference. Zeolite Y has an empirical formulaexpressed in terms of moles of oxides of:

0.9+−0.2 Na₂O:Al₂O₃:wSiO₂:xH₂O

where “w” has a value of greater than 3 up to about 6 and “x” has avalue up to 9. As with zeolite X, a reaction mixture containing theappropriate ratio of materials is prepared, and then reacted at atemperature of about 20° C. to about 125° C. for a time of about 16hours to about 8 days.

The nickel or molybdenum forms of zeolites X and Y can be prepared byion exchange methods well known in the art. Ion exchange can be carriedout in a batch or continuous process with a continuous processpreferred. The metal salts which can be used to carry out the exchangeinclude nickel chloride, nickel nitrate, and sodium molybdate.

Yet another set of adsorbents is the group of clays which make up thesmectite family of clays and which have a surface area of at least 150m²/g. Clays are composed of infinite layers (lamellae) of metal oxidesand hydroxides stacked one on top of the other. These layers or sheetsare composed of tetrahedrally coordinated cations which are linkedthrough shared oxygens to sheets of cations octahedrally coordinated tooxygens and hydroxyls. When one octahedral sheet is linked to onetetrahedral sheet a 1:1 layered structure is formed as in kaolinite,whereas when one octahedral sheet is linked to two tetrahedral sheets, a2:1 layered structure is produced as in beidellite. Anionic charges onthe tetrahedral layers (usually siliceous layers) are neutralized bycations such as Na⁺ or Ca⁺² in the interlamellar spaces. These cationscan be exchanged with other cations.

The smectite clays are 2:1 layered swellable clays. By swellable ismeant that the clays swell or expand when placed in water or othersolvents. Specific smectite clays are montmorillonite, beidellite,nontronite, hectorite, saponite and sauconite.

Contacting of the liquid hydrocarbon stream with any of the adsorbentsdescribed above can be carried out by means well known in the art. Forexample, the contacting can be carried out in a batch mode or in acontinuous mode. In a batch mode, the stream to be treated is mixed witha sufficient amount of adsorbent in an appropriate size reaction vessel.The resultant mixture can be stirred or agitated to ensure completecontact of the stream with the adsorbent. In order to ensure that thesulfur compounds are completely adsorbed onto the support, it isnecessary that the hydrocarbon stream be contacted with the solidsolution for a time of about 10 minutes to about 10 hours. If acontinuous process is used, the adsorbent is placed in a vertical columnand the stream to be treated is upflowed through the column. The streamis flowed at a liquid hourly space velocity of about 0.1 hr⁻¹ to about10 hr⁻¹.

Whether the process is carried out in a batch or continuous manner, theadsorbent can be used in the form of extrudates, pills, beads, spheres,etc. Usually, the adsorbent is mixed with a binder such as attapulgiteclay, minugel clay and bentonite clay and then formed into the desiredshape. The amount of binder which is used varies from about 8 to about20 wt. %. Processes for forming the various shapes are well known in theart.

Finally, the contacting can be carried out over a broad temperaturerange. Generally the temperature range is from about 10° C. to about100° C., or about 20° C. to about 70° C. The process is conducted atatmospheric pressure or pressures up to about 1379 kPa (g) (about 200psig).

The second mercaptan lean stream 525 from the adsorption zone 520 can becombined with the low boiling first mercaptan lean stream 505, and/orthe high boiling first mercaptan lean stream 515 to form a combinedmercaptan lean stream 530. In some embodiments, the light fraction 140can be combined with one or more of these streams as well.

Alternatively, the liquid stream 175 can be separated into a mercaptanrich stream and a mercaptan lean stream as described above in FIG. 1,rather than a mercaptan rich stream and at least two mercaptan leanstreams.

In the embodiment shown in FIG. 5, the mercaptan rich stream is treatedusing an ionic liquid.

The FCC naphtha feed 105 is hydrogenated in the selective hydrogenationzone 115, separated into a light fraction 140 and a heavy fraction 145in splitter column 135, desulfurized in selective hydrodesulfurizationzone 155, separated into hydrogen-rich stream 170 and liquid stream 175in the same way as described above with respect to FIG. 1.

The liquid stream 175 is sent to the fractionation zone 180 where it isseparated into a low boiling first mercaptan lean stream 605, amercaptan rich stream 610, and a high boiling first mercaptan leanstream 615.

The mercaptan rich stream 610 is sent to an ionic liquid extraction zone620 along with lean ionic liquid stream 625. The lean ionic liquidstream 625 can include fresh ionic liquid and/or regenerated ionicliquid.

Ionic liquids suitable for use in the instant invention arenaphtha-immiscible ionic liquids. As used herein the term“naphtha-immiscible ionic liquid” means the ionic liquid is capable offorming a separate phase from naphtha under the operating conditions ofthe process. Ionic liquids that are miscible with naphtha at the processconditions will be completely soluble with the naphtha; therefore, nophase separation will be feasible. Thus, naphtha-immiscible ionicliquids may be insoluble with or partially soluble with the hydrocarbonfeed under the operating conditions. An ionic liquid capable of forminga separate phase from the naphtha under the operating conditions isconsidered to be naphtha-immiscible. Ionic liquids according to theinvention may be insoluble, partially soluble, or completely soluble(miscible) with water.

The ionic liquid can be any acidic ionic liquid. There can be one ormore ionic liquids. The ionic liquid comprises an organic cation and ananion. Suitable cations include, but are not limited to,nitrogen-containing cations and phosphorus-containing cations. Suitableorganic cations include, but are not limited to:

where R¹-R²¹ are independently selected from C₁-C₂₀ hydrocarbons, C₁-C₂₀hydrocarbon derivatives, halogens, and H. Suitable hydrocarbons andhydrocarbon derivatives include saturated and unsaturated hydrocarbons,halogen substituted and partially substituted hydrocarbons and mixturesthereof. C₁-C₈ hydrocarbons are particularly suitable.

The anion can be derived from halides, typically halometallates, andcombinations thereof. The anion is typically derived from metal andnonmetal halides, such as metal and nonmetal chlorides, bromides,iodides, fluorides, or combinations thereof. Combinations of halidesinclude, but are not limited to, mixtures of two or more metal ornonmetal halides (e.g., AlCl₄ ⁻ and BF₄ ⁻), and mixtures of two or morehalides with a single metal or nonmetal (e.g., AlCl₃Br⁻). In someembodiments, the metal is aluminum, with the mole fraction of aluminumranging from 0<Al<0.25 in the anion. Suitable anions include, but arenot limited to, AlCl₄ ⁻, Al₂Cl₇ ⁻, Al₃Cl₁₀ ⁻, AlCl₃Br⁻, Al₂Cl₆Br⁻,Al₃Cl₉Br⁻, AlBr₄ ⁻, Al₂Br₇ ⁻, Al₃Br₁₀ ⁻, GaCl₄ ⁻, Ga₂Cl₇ ⁻, Ga₃Cl₁₀ ⁻,GaCl₃Br⁻, Ga₂Cl₆Br⁻, Ga₃Cl₉Br⁻, CuCl₂ ⁻, Cu₂Cl₃ ⁻, Cu₃Cl₄ ⁻, ZnCl₃ ⁻,FeCl₃ ⁻, FeCl₄ ⁻, Fe₃Cl₇ ⁻, PF₆ ⁻, and BF4⁻.

The mercaptan removal step may be conducted under mercaptan removalconditions including temperatures and pressures sufficient to keep theionic liquid and naphtha feeds and effluents as liquids. For example,the mercaptan removal step temperature may range between about 10° C.and less than the decomposition temperature of the ionic liquid, and thepressure may range between about atmospheric pressure and about 700 kPa(g). When the ionic liquid comprises more than one ionic liquidcomponent, the decomposition temperature of the ionic liquid is thelowest temperature at which any of the ionic liquid componentsdecompose. The mercaptan removal step may be conducted at a uniformtemperature and pressure or the contacting and separating steps of themercaptan removal step may be operated at different temperatures and/orpressures. In an embodiment, the contacting step is conducted at a firsttemperature, and the separating step is conducted at a temperature atleast 5° C. lower than the first temperature. Such temperaturedifferences may facilitate separation of the naphtha and ionic liquidphases.

The mercaptan removal step conditions such as the contacting or mixingtime, the separation or settling time, and the ratio of the mercaptanrich stream 610 to the lean ionic liquid stream 625 may vary greatlybased, for example, on the specific ionic liquid or liquids employed,the nature of the naphtha feed (straight run or previously processed),the sulfur content of the naphtha feed, the degree of sulfur removalrequired, the number of sulfur removal steps employed, and the specificequipment used. In general it is expected that contacting time may rangefrom less than one minute to about two hours; settling time may rangefrom about one minute to about eight hours; and the weight ratio ofnaphtha feed to lean ionic liquid introduced to the sulfur removal stepmay range from 1:10,000 to 10,000:1. In an embodiment, the weight ratioof naphtha feed to lean ionic liquid may range from about 1:1,000 toabout 1,000:1; and the weight ratio of naphtha feed to lean ionic liquidmay range from about 1:100 to about 100:1. In an embodiment the weightof naphtha feed is greater than the weight of ionic liquid introduced tothe sulfur removal step.

The mercaptan rich stream 610 and the lean ionic liquid stream 625 arecontacted forming the second mercaptan lean stream 630, and a mercaptanrich ionic liquid stream 635 containing mercaptan compounds.

In one embodiment, the ionic liquid extraction zone 620 includes acontacting zone with a mixer/settler in which the mercaptan rich stream610 and the lean ionic liquid stream 625 are mixed and then allowedsettle, forming two phases: an ionic liquid phase and a naphtha phase.

In another embodiment, the ionic liquid extraction zone 620 includes acountercurrent extraction column. The mercaptan rich stream 610 and thelean ionic liquid stream 625 flow countercurrently and the mercaptancompounds are transferred from the mercaptan rich stream to the ionicliquid.

The ionic liquid extraction zone 620 can include an optional waterwashing zone to recover ionic liquid that is entrained or otherwiseremains in the naphtha. The water washing step can be performed usingany suitable equipment and conditions used to conduct otherliquid-liquid wash and extraction operations.

If desired, the mercaptan rich ionic liquid stream 635 can be sent to anoptional regeneration zone to regenerate the rich ionic liquid byremoving the mercaptan compounds from the ionic liquid. The rich ionicliquid can be regenerated in any suitable manner. A variety of methodsfor regenerating ionic liquids have been developed. For example, U.S.Pat. No. 7,651,970; U.S. Pat. No. 7,825,055; U.S. Pat. No. 7,956,002;U.S. Pat. No. 7,732,363, each of which is incorporated herein byreference, describe contacting ionic liquid containing the conjunctpolymer with a reducing metal (e.g., Al), an inert hydrocarbon (e.g.,hexane), and hydrogen and heating to about 100° C. to transfer theconjunct polymer to the hydrocarbon phase, allowing for the conjunctpolymer to be removed from the ionic liquid phase. Another methodinvolves contacting ionic liquid containing conjunct polymer with areducing metal (e.g., Al) in the presence of an inert hydrocarbon (e.g.hexane) and heating to about 100° C. to transfer the conjunct polymer tothe hydrocarbon phase, allowing for the conjunct polymer to be removedfrom the ionic liquid phase. See e.g., U.S. Pat. No. 7,674,739 B2; whichis incorporated herein by reference. Still another method ofregenerating the ionic liquid involves contacting the ionic liquidcontaining the conjunct polymer with a reducing metal (e.g., Al), HCl,and an inert hydrocarbon (e.g. hexane), and heating to about 100° C. totransfer the conjunct polymer to the hydrocarbon phase. See e.g., U.S.Pat. No. 7,727,925, which is incorporated herein by reference. The ionicliquid can be regenerated by adding a homogeneous metal hydrogenationcatalyst (e.g., (PPh₃)₃RhCl) to ionic liquid containing conjunct polymerand an inert hydrocarbon (e.g. hexane), and introducing hydrogen. Theconjunct polymer is reduced and transferred to the hydrocarbon layer.See e.g., U.S. Pat. No. 7,678,727, which is incorporated herein byreference. Another method for regenerating the ionic liquid involvesadding HCl, isobutane, and an inert hydrocarbon to the ionic liquidcontaining the conjunct polymer and heating to about 100° C. Theconjunct polymer reacts to form an uncharged complex, which transfers tothe hydrocarbon phase. See e.g., U.S. Pat. No. 7,674,740, which isincorporated herein by reference. The ionic liquid could also beregenerated by adding a supported metal hydrogenation catalyst (e.g.Pd/C) to the ionic liquid containing the conjunct polymer and an inerthydrocarbon (e.g. hexane). Hydrogen is introduced and the conjunctpolymer is reduced and transferred to the hydrocarbon layer. See e.g.,U.S. Pat. No. 7,691,771, which is incorporated herein by reference.Still another method involves adding a suitable substrate (e.g.pyridine) to the ionic liquid containing the conjunct polymer. After aperiod of time, an inert hydrocarbon is added to wash away the liberatedconjunct polymer. The ionic liquid precursor [butylpyridinium][Cl] isadded to the ionic liquid (e.g. [butylpyridinium][Al₂Cl₇]) containingthe conjunct polymer followed by an inert hydrocarbon. After mixing, thehydrocarbon layer is separated, resulting in a regenerated ionic liquid.See, e.g., U.S. Pat. No. 7,737,067, which is incorporated herein byreference. Another method involves adding ionic liquid containingconjunct polymer to a suitable substrate (e.g. pyridine) and anelectrochemical cell containing two aluminum electrodes and an inerthydrocarbon. A voltage is applied, and the current measured to determinethe extent of reduction. After a given time, the inert hydrocarbon isseparated, resulting in a regenerated ionic liquid. See, e.g., U.S. Pat.No. 8,524,623, which is incorporated herein by reference. Ionic liquidscan also be regenerated by contacting with silane compounds (U.S.application Ser. No. 14/269,943), borane compounds (U.S. applicationSer. No. 14/269,978), Brønsted acids, (U.S. application Ser. No.14/229,329), or C₁ to C₁₀ Paraffins (U.S. application Ser. No.14/229,403), each of which is incorporated herein by reference.

The second mercaptan lean stream 630 can be combined with the lowboiling first mercaptan lean stream 605, and/or the high boiling firstmercaptan lean stream 615 to form a combined mercaptan lean stream 640.In some embodiments, the light fraction 140 can be combined with one ormore of these streams as well.

Alternatively, the liquid stream 175 can be separated into a mercaptanrich stream and a mercaptan lean stream as described above in FIG. 1,rather than a mercaptan rich stream and at least two mercaptan leanstreams.

By the term “about,” we mean that within 10% of the specified value, orwithin 5%, or within 1%.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention. It being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims.

SPECIFIC EMBODIMENTS

While the following is described in conjunction with specificembodiments, it will be understood that this description is intended toillustrate and not limit the scope of the preceding description and theappended claims.

A first embodiment of the invention is a process for reducing the sulfurcontent of full range naphtha comprising introducing a naphtha feed intoa selective hydrogenation zone in the presence of hydrogen and ahydrogenation catalyst under selective hydrogenation conditions to forma hydrogenated feed; separating the hydrogenated feed into at least twofractions, a light fraction and a heavy fraction; introducing the heavyfraction to a selective hydrodesulfurization zone in the presence ofhydrogen and a hydrodesulfurization catalyst under selectivehydrodesulfurization conditions to form a desulfurized stream, thedesulfurized stream containing mercaptans; separating at least a portionof the desulfurized stream into at least two streams, a mercaptan richstream and a first mercaptan lean stream; and treating at least aportion of the mercaptan rich stream to remove at least a portion of themercaptan compounds to form a second mercaptan lean stream. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the first embodiment in this paragraph whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the mercaptan rich stream into at least one of a causticextraction zone, a hydrodesulfurization reaction zone, the selectivehydrogenation zone, an adsorption zone, and an ionic liquid extractionzone. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph further comprising combining the first mercaptan lean streamwith the second mercaptan lean stream. An embodiment of the invention isone, any or all of prior embodiments in this paragraph up through thefirst embodiment in this paragraph further comprising combining thelight fraction with at least one of the first mercaptan lean stream andthe second mercaptan lean stream. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the firstembodiment in this paragraph wherein separating the at least the portionof the desulfurized stream into at least two streams comprisesseparating the at least the portion of the desulfurized stream into themercaptan rich stream and the first mercaptan lean stream. An embodimentof the invention is one, any or all of prior embodiments in thisparagraph up through the first embodiment in this paragraph wherein themercaptan rich stream has a boiling point in a range of about 60° C. toabout 100° C., and the first mercaptan lean stream has a boiling pointin a range of about 100° C. to about 220° C. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph wherein separating the atleast the portion of the desulfurized stream into at least two streamscomprises separating the at least the portion of the desulfurized streaminto the mercaptan rich stream and at least two first mercaptan leanstreams, a low boiling first mercaptan lean stream having a boilingpoint range lower than a boiling point range of the mercaptan richstream and a high boiling first mercaptan stream having a boiling pointrange greater than the boiling point range of the mercaptan rich stream.An embodiment of the invention is one, any or all of prior embodimentsin this paragraph up through the first embodiment in this paragraphwherein the mercaptan rich stream has a boiling point in a range ofabout 85° C. to about 100° C., and the low boiling first mercaptan leanstream has a boiling point in a range of about 60° C. to about 85° C.,and the high boiling first mercaptan lean stream has a boiling point ina range of about 100° C. to about 220° C. An embodiment of the inventionis one, any or all of prior embodiments in this paragraph up through thefirst embodiment in this paragraph wherein the mercaptan rich stream hasa boiling point in a range of about 60° C. to about 100° C. and thefirst mercaptan lean stream has a boiling point in a range of about 100°C. to about 220° C., and wherein treating the mercaptan rich streamcomprises introducing the mercaptan rich stream into a causticextraction zone. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the first embodiment inthis paragraph and further comprising separating the desulfurized streaminto a gas stream and a liquid stream in a first side of a divided wallseparator and wherein separating the at least the portion of thedesulfurized stream into the at least two streams comprises separatingthe liquid stream into at least the mercaptan rich stream and at leasttwo first mercaptan lean streams, wherein the mercaptan rich stream hasa boiling point in a range of about 85° C. to about 100° C., and the atleast two first mercaptan lean streams comprise a low boiling firstmercaptan lean stream having a boiling point in a range of about 60° C.to about 85° C., and a high boiling mercaptan lean stream having aboiling point in a range of about 100° C. to about 220° C., and whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing at least the portion of the mercaptan rich stream into ahydrodesulfurization reaction zone forming a hydrodesulfurizationreaction zone effluent; and further comprising separating thehydrodesulfurization reaction zone effluent into a gas stream and aliquid stream in the second side of the divided wall separator;stripping the liquid stream in a stripping zone to form a thirdmercaptan lean stream. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the first embodimentin this paragraph wherein separating the at least the portion of thedesulfurized stream into at least two streams comprises separating theat least the portion of the desulfurized stream into at least themercaptan rich stream and at least two mercaptan lean streams, whereinthe mercaptan rich stream has a boiling point in a range of about 85° C.to about 100° C., and the at least two first mercaptan lean streamscomprise a low boiling first mercaptan lean stream having a boilingpoint in a range of about 60° C. to about 85° C., and a high boilingmercaptan lean stream having a boiling point in a range of about 100° C.to about 220° C., and wherein treating the at least the portion of themercaptan rich stream comprises introducing the at least the portion ofthe mercaptan rich stream into the selective hydrogenation zone. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the first embodiment in this paragraph whereinseparating at least the portion of the desulfurized stream into at leasttwo streams comprises separating at least the portion of thedesulfurized stream into at least the mercaptan rich stream and at leasttwo mercaptan lean streams, wherein the mercaptan rich stream has aboiling point in a range of about 85° C. to about 100° C., and the atleast two first mercaptan lean streams comprise a low boiling firstmercaptan lean stream having a boiling point in a range of about 60° C.to about 85° C., and a high boiling mercaptan lean stream having aboiling point in a range of about 100° C. to about 220° C., and whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the at least the portion of the mercaptan rich stream intoan adsorption zone. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the first embodiment inthis paragraph wherein separating at least the portion of thedesulfurized stream into at least two streams comprises separating atleast the portion of the desulfurized stream into at least the mercaptanrich stream and at least two mercaptan lean streams, wherein themercaptan rich stream has a boiling point in a range of about 85° C. toabout 100° C., and the at least two first mercaptan lean streamscomprise a low boiling first mercaptan lean stream having a boilingpoint in a range of about 60° C. to about 85° C., and a high boilingmercaptan lean stream having a boiling point in a range of about 100° C.to about 220° C., and wherein treating the at least the portion of themercaptan rich stream comprising introducing the at least the portion ofthe mercaptan rich stream into an ionic liquid extraction zone.

A second embodiment of the invention is a process for reducing thesulfur content of full range FCC naphtha comprising introducing a FCCnaphtha feed into a selective hydrogenation zone in the presence ofhydrogen and a hydrogenation catalyst under selective hydrogenationconditions to form a hydrogenated feed; separating the hydrogenated feedinto at least two fractions, a lighter fraction and a heavier fraction;introducing the heavier fraction to a selective hydrodesulfurizationzone in the presence of hydrogen and a hydrodesulfurization catalystunder selective hydrodesulfurization conditions to form a desulfurizedstream, the desulfurized stream containing mercaptans; separating atleast a portion of the desulfurized stream into at least two streams, amercaptan rich stream and a first mercaptan lean stream; and treating atleast a portion of the mercaptan rich stream to remove at least aportion of the mercaptan compounds to form a second mercaptan leanstream, wherein treating the at least the portion of the mercaptan richstream comprises introducing the at least the portion of the mercaptanrich stream into at least one of a caustic extraction zone, ahydrodesulfurization reaction zone, the selective hydrogenation zone, anadsorption zone, and an ionic liquid extraction zone. An embodiment ofthe invention is one, any or all of prior embodiments in this paragraphup through the second embodiment in this paragraph further comprising atleast one of combining the first mercaptan lean stream with the secondmercaptan lean stream; and combining the lighter fraction with at leastone of the first mercaptan lean stream and the second mercaptan leanstream. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the second embodiment in thisparagraph wherein separating the at least the portion of thedesulfurized stream into at least two streams comprises separating theat least the portion of the desulfurized stream into the mercaptan richstream and the first mercaptan lean stream. The process of claim 16wherein the mercaptan rich stream has a boiling point about 60° C. toabout 100° C. and the first mercaptan lean stream has a boiling point ina range of about 100° C. to about 220° C. An embodiment of the inventionis one, any or all of prior embodiments in this paragraph up through thesecond embodiment in this paragraph wherein separating the at least theportion of the desulfurized stream into at least two streams comprisesseparating the at least the portion of the desulfurized stream into themercaptan rich stream and at least two first mercaptan lean streams, alow boiling first mercaptan lean stream having a boiling point rangelower than a boiling point range of the mercaptan rich stream and a highboiling first mercaptan stream having a boiling point range greater thanthe boiling range of the mercaptan rich stream. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the second embodiment in this paragraph wherein the boilingpoint range of the mercaptan rich stream is about 85° C. to about 100°C., and the boiling point range of the low boiling first mercaptan leanstream is about 60° C. to about 85° C., and the boiling point range ofthe high boiling first mercaptan lean stream is about 100° C. to about220° C.

A third embodiment of the invention is a process for reducing the sulfurcontent of full range FCC naphtha comprising introducing a FCC naphthafeed into a selective hydrogenation zone in the presence of hydrogen anda hydrogenation catalyst under selective hydrogenation conditions toform a hydrogenated feed; separating the hydrogenated feed into at leasttwo fractions, a lighter fraction and a heavier fraction; introducingthe heavier fraction to a selective hydrodesulfurization zone in thepresence of hydrogen and a hydrodesulfurization catalyst under selectivehydrodesulfurization conditions to form a desulfurized stream, thedesulfurized stream containing mercaptans; separating at least a portionof the desulfurized stream into at least a mercaptan rich stream, a lowboiling mercaptan lean stream having a boiling point range lower than aboiling point range of the mercaptan rich stream, and a high boilingfirst mercaptan stream having a boiling point range greater than theboiling range of the mercaptan rich stream; and treating at least aportion of the mercaptan rich stream to remove at least a portion of themercaptan compounds to form a second mercaptan lean stream, whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the at least the portion of the mercaptan rich stream intoat least one of a caustic extraction zone, a hydrodesulfurizationreaction zone, the selective hydrogenation zone, an adsorption zone, andan ionic liquid extraction zone.

Without further elaboration, it is believed that using the precedingdescription that one skilled in the art can utilize the presentinvention to its fullest extent and easily ascertain the essentialcharacteristics of this invention, without departing from the spirit andscope thereof, to make various changes and modifications of theinvention and to adapt it to various usages and conditions. Thepreceding preferred specific embodiments are, therefore, to be construedas merely illustrative, and not limiting the remainder of the disclosurein any way whatsoever, and that it is intended to cover variousmodifications and equivalent arrangements included within the scope ofthe appended claims.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

What is claimed is:
 1. A process for reducing the sulfur content of fullrange naphtha comprising: introducing a naphtha feed into a selectivehydrogenation zone in the presence of hydrogen and a hydrogenationcatalyst under selective hydrogenation conditions to form a hydrogenatedfeed; separating the hydrogenated feed into at least two fractions, alight fraction and a heavy fraction; introducing the heavy fraction to aselective hydrodesulfurization zone in the presence of hydrogen and ahydrodesulfurization catalyst under selective hydrodesulfurizationconditions to form a desulfurized stream, the desulfurized streamcontaining mercaptans; separating at least a portion of the desulfurizedstream into at least two streams, a mercaptan rich stream and a firstmercaptan lean stream; and treating at least a portion of the mercaptanrich stream to remove at least a portion of the mercaptan compounds toform a second mercaptan lean stream.
 2. The process of claim 1 whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the mercaptan rich stream into at least one of a causticextraction zone, a hydrodesulfurization reaction zone, the selectivehydrogenation zone, an adsorption zone, and an ionic liquid extractionzone.
 3. The process of claim 1 further comprising combining the firstmercaptan lean stream with the second mercaptan lean stream.
 4. Theprocess of claim 1 further comprising combining the light fraction withat least one of the first mercaptan lean stream and the second mercaptanlean stream.
 5. The process of claim 1 wherein separating the at leastthe portion of the desulfurized stream into at least two streamscomprises separating the at least the portion of the desulfurized streaminto the mercaptan rich stream and the first mercaptan lean stream. 6.The process of claim 5 wherein the mercaptan rich stream has a boilingpoint in a range of about 60° C. to about 100° C., and the firstmercaptan lean stream has a boiling point in a range of about 100° C. toabout 220° C.
 7. The process of claim 1 wherein separating the at leastthe portion of the desulfurized stream into at least two streamscomprises separating the at least the portion of the desulfurized streaminto the mercaptan rich stream and at least two first mercaptan leanstreams, a low boiling first mercaptan lean stream having a boilingpoint range lower than a boiling point range of the mercaptan richstream and a high boiling first mercaptan stream having a boiling pointrange greater than the boiling point range of the mercaptan rich stream.8. The process of claim 7 wherein the mercaptan rich stream has aboiling point in a range of about 85° C. to about 100° C., and the lowboiling first mercaptan lean stream has a boiling point in a range ofabout 60° C. to about 85° C., and the high boiling first mercaptan leanstream has a boiling point in a range of about 100° C. to about 220° C.9. The process of claim 1 wherein the mercaptan rich stream has aboiling point in a range of about 60° C. to about 100° C. and the firstmercaptan lean stream has a boiling point in a range of about 100° C. toabout 220° C., and wherein treating the mercaptan rich stream comprisesintroducing the mercaptan rich stream into a caustic extraction zone.10. The process of claim 1 and further comprising: separating thedesulfurized stream into a gas stream and a liquid stream in a firstside of a divided wall separator and wherein separating the at least theportion of the desulfurized stream into the at least two streamscomprises separating the liquid stream into at least the mercaptan richstream and at least two first mercaptan lean streams, wherein themercaptan rich stream has a boiling point in a range of about 85° C. toabout 100° C., and the at least two first mercaptan lean streamscomprise a low boiling first mercaptan lean stream having a boilingpoint in a range of about 60° C. to about 85° C., and a high boilingmercaptan lean stream having a boiling point in a range of about 100° C.to about 220° C., and wherein treating the at least the portion of themercaptan rich stream comprises introducing at least the portion of themercaptan rich stream into a hydrodesulfurization reaction zone forminga hydrodesulfurization reaction zone effluent; and further comprising:separating the hydrodesulfurization reaction zone effluent into a gasstream and a liquid stream in the second side of the divided wallseparator; stripping the liquid stream in a stripping zone to form athird mercaptan lean stream.
 11. The process of claim 1 whereinseparating the at least the portion of the desulfurized stream into atleast two streams comprises separating the at least the portion of thedesulfurized stream into at least the mercaptan rich stream and at leasttwo mercaptan lean streams, wherein the mercaptan rich stream has aboiling point in a range of about 85° C. to about 100° C., and the atleast two first mercaptan lean streams comprise a low boiling firstmercaptan lean stream having a boiling point in a range of about 60° C.to about 85° C., and a high boiling mercaptan lean stream having aboiling point in a range of about 100° C. to about 220° C., and whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the at least the portion of the mercaptan rich stream intothe selective hydrogenation zone.
 12. The process of claim 1 whereinseparating at least the portion of the desulfurized stream into at leasttwo streams comprises separating at least the portion of thedesulfurized stream into at least the mercaptan rich stream and at leasttwo mercaptan lean streams, wherein the mercaptan rich stream has aboiling point in a range of about 85° C. to about 100° C., and the atleast two first mercaptan lean streams comprise a low boiling firstmercaptan lean stream having a boiling point in a range of about 60° C.to about 85° C., and a high boiling mercaptan lean stream having aboiling point in a range of about 100° C. to about 220° C., and whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the at least the portion of the mercaptan rich stream intoan adsorption zone.
 13. The process of claim 1 wherein separating atleast the portion of the desulfurized stream into at least two streamscomprises separating at least the portion of the desulfurized streaminto at least the mercaptan rich stream and at least two mercaptan leanstreams, wherein the mercaptan rich stream has a boiling point in arange of about 85° C. to about 100° C., and the at least two firstmercaptan lean streams comprise a low boiling first mercaptan leanstream having a boiling point in a range of about 60° C. to about 85°C., and a high boiling mercaptan lean stream having a boiling point in arange of about 100° C. to about 220° C., and wherein treating the atleast the portion of the mercaptan rich stream comprising introducingthe at least the portion of the mercaptan rich stream into an ionicliquid extraction zone.
 14. A process for reducing the sulfur content offull range FCC naphtha comprising: introducing a FCC naphtha feed into aselective hydrogenation zone in the presence of hydrogen and ahydrogenation catalyst under selective hydrogenation conditions to forma hydrogenated feed; separating the hydrogenated feed into at least twofractions, a lighter fraction and a heavier fraction; introducing theheavier fraction to a selective hydrodesulfurization zone in thepresence of hydrogen and a hydrodesulfurization catalyst under selectivehydrodesulfurization conditions to form a desulfurized stream, thedesulfurized stream containing mercaptans; separating at least a portionof the desulfurized stream into at least two streams, a mercaptan richstream and a first mercaptan lean stream; and treating at least aportion of the mercaptan rich stream to remove at least a portion of themercaptan compounds to form a second mercaptan lean stream, whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the at least the portion of the mercaptan rich stream intoat least one of a caustic extraction zone, a hydrodesulfurizationreaction zone, the selective hydrogenation zone, an adsorption zone, andan ionic liquid extraction zone.
 15. The process of claim 14 furthercomprising at least one of: combining the first mercaptan lean streamwith the second mercaptan lean stream; and combining the lighterfraction with at least one of the first mercaptan lean stream and thesecond mercaptan lean stream.
 16. The process of claim 14 whereinseparating the at least the portion of the desulfurized stream into atleast two streams comprises separating the at least the portion of thedesulfurized stream into the mercaptan rich stream and the firstmercaptan lean stream.
 17. The process of claim 16 wherein the mercaptanrich stream has a boiling point about 60° C. to about 100° C. and thefirst mercaptan lean stream has a boiling point in a range of about 100°C. to about 220° C.
 18. The process of claim 14 wherein separating theat least the portion of the desulfurized stream into at least twostreams comprises separating the at least the portion of thedesulfurized stream into the mercaptan rich stream and at least twofirst mercaptan lean streams, a low boiling first mercaptan lean streamhaving a boiling point range lower than a boiling point range of themercaptan rich stream and a high boiling first mercaptan stream having aboiling point range greater than the boiling range of the mercaptan richstream.
 19. The process of claim 18 wherein the boiling point range ofthe mercaptan rich stream is about 85° C. to about 100° C., and theboiling point range of the low boiling first mercaptan lean stream isabout 60° C. to about 85° C., and the boiling point range of the highboiling first mercaptan lean stream is about 100° C. to about 220° C.20. A process for reducing the sulfur content of full range FCC naphthacomprising: introducing a FCC naphtha feed into a selectivehydrogenation zone in the presence of hydrogen and a hydrogenationcatalyst under selective hydrogenation conditions to form a hydrogenatedfeed; separating the hydrogenated feed into at least two fractions, alighter fraction and a heavier fraction; introducing the heavierfraction to a selective hydrodesulfurization zone in the presence ofhydrogen and a hydrodesulfurization catalyst under selectivehydrodesulfurization conditions to form a desulfurized stream, thedesulfurized stream containing mercaptans; separating at least a portionof the desulfurized stream into at least a mercaptan rich stream, a lowboiling mercaptan lean stream having a boiling point range lower than aboiling point range of the mercaptan rich stream, and a high boilingfirst mercaptan stream having a boiling point range greater than theboiling range of the mercaptan rich stream; and treating at least aportion of the mercaptan rich stream to remove at least a portion of themercaptan compounds to form a second mercaptan lean stream, whereintreating the at least the portion of the mercaptan rich stream comprisesintroducing the at least the portion of the mercaptan rich stream intoat least one of a caustic extraction zone, a hydrodesulfurizationreaction zone, the selective hydrogenation zone, an adsorption zone, andan ionic liquid extraction zone.